1. Field of the Invention
This invention relates to a motor provided with output transmitting means on a rotor which can be constructed super-compactly.
2. Related Background Art
What are formed as compact motors include, for example, what is shown in FIG. 23 of the accompanying drawings as a compact cylinder type step motor. A stator coil 105 is wound on a bobbin 101 concentrically therewith, the bobbin 101 is sandwiched and fixed between two stator yokes 106 from the axial direction thereof and stator teeth 106a and stator teeth 106b are alternately disposed on the stator yokes 106 in the circumferential direction of the inner diametral surface of the bobbin 101, and the stator yokes 106 integral with the stator teeth 106a or 106b are fixed to cases 103, whereby a stator 102 is constructed.
A flange 115 and a bearing 108 are fixed to one of two sets of cases 103, and another bearing 108 is fixed to the other case 103. A rotor 109 comprises a rotor magnet 111 fixed to a rotor shaft 110, and the rotor magnet 111 formes a radial clearance portion with the stator yokes 106 of the stator 102. The rotor shaft 110 is rotatably supported between two bearings 108.
However, the above-described compact step motor according to the prior art has the cases 103, the bobbin 101, the stator coil 105 and the stator yokes 106 concentrically disposed on the outer periphery of the rotor and therefore has the disadvantage that the outer dimension of the motor becomes large. Also, the magnetic flux created by the supply of electric power to the stator coil 105 passes chiefly the end surface 106a1 of the stator teeth 106a and the end surface 106b1 of the stator teeth 106b as shown in FIG. 24 of the accompanying drawings and therefore does not effectively act on the rotor magnet 111, and this has led to the disadvantage that the output of the motor does not become high.
The applicant has previously proposed a motor which has solved such problems in U.S. patent application Ser. No. 08/831,863.
This proposed motor is constructed in such a manner that a rotor comprising a permanent magnet equally divided in the circumferential direction thereof and alternately magnetized to different poles is formed into a cylindrical shape, a first coil, the rotor and a second coil are successively disposed axially of the rotor, a first outer magnetic pole and a first inner magnetic pole excited by the first coil are opposed to the outer peripheral surface and the inner peripheral surface of the rotor, and a second outer magnetic pole and a second inner magnetic pole excited by the second coil are opposed to the outer peripheral surface and the inner peripheral surface of the rotor, and a rotary shaft, which is a rotor shaft, is taken out of the cylindrically shaped permanent magnet.
The motor of such construction can be made high in output and small in its outer dimension, but since the diametral dimension of the inner magnetic pole is small, it has been difficult to work the teeth of the magnetic pole, and since the rotary shaft taken out of the cylindrically shaped permanent magnet is also small, it has also been difficult to work the rotor provided with the rotary shaft.
Therefore, the applicant has recently proposed in U.S. patent application Ser. No. 08/994,994 a motor in which the shape of an inner magnetic pole is made into a shape of good workability (the applicant has also proposed in U.S. patent application the number of which is not yet assigned a motor in which a rotor provided with a rotary shaft has also been made easily workable), but there has been desired a rotor in which output transmitting means, such as a gear or a pulley can be easily mounted on a rotary shaft of a small diametral dimension and a stable output free of vibration can be obtained.